BME103:T130 Group 5
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(→Research and Development)
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Revision as of 17:24, 14 November 2012
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Lab Write-Up 1
Lab Write-Up 2
Lab Write-Up 3
Course Logistics For Instructors
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LAB 1 WRITE-UP
Initial Machine Testing
The Original Design
When the wire from the board for the LCD screen was unplugged from the main board, the LCD screen on the machine turned off and went blank.
When the white wire that connects the main board of the machine and the temperature system was unplugged, the temperature reading decreased and was not accurate.
Polymerase Chain Reaction
Polymerase Chain Reaction (PCR) is a process that uses DNA polymerase to synthesize a large number of copies of a target DNA sequence. PCR is dependent on short DNA fragments called primers. After the DNA has been denatured by heating and then cooled to a temperature suitable for the primers to bind to their complementary sequences, the primers bind to areas adjacent to each side of the targeted DNA sequence. Once the primers are in place, the polymerase extends them into large complimentary strands. The DNA is then denatured once again, then cooled, the primers bind to the complimentary sequence and then the polymerase extends them. Repeating this process results in an exponential amplification of the target DNA sequence.
(Add your work from Week 3, Part 2 here)
Research and Development
Specific Cancer Marker Detection - The Underlying Technology
The sequence r17879961 represents a specific sequence where a Thymine is replaced by Cytosine due to a missense mutation on chromosome 22. It affects gene CHK2 that is linked to colorectal cancer. A primer binds to a specific sequence on the template DNA and tells Taq polymerase where to begin reading and adding nucleotides to synthesize a new strand of DNA. Primers are very specific in that they can only bind to a certain sequence. A backwards primer consists of 20 nucleotides that specifically are ACT TCT TAC ATT CGA TAC AT. The forward primer is TGT GAT CTT CTA TGT ATG CA. These primers will only bind to that specific sequence of r17879961 where the Cytosine is present and not the Thymine.
If the sequence is present, the primers will bind to both leading and lagging strands of the template DNA. Taq polymerase can then bind and begin synthesizing the strand. The test will come out positive because the DNA will synthesize to create double stranded DNA that the SYBR Green I dye will then bind to. This will cause the DNA to fluoresce and yield a positive result.
If the r1789961 SNP is not present, the primer will not bind to the DNA template. Because the primers tell Taq polymerase where to replicate, Taq polymerase will not have anywhere to bind. Replication will not occur with the product of a double-stranded DNA, but linearly. The SYBR Green I dye only binds to double-stranded DNA, so it will not show because it is single-stranded. There would not be enough double-stranded DNA to fluoresce if the cancer gene is not present. Therefore, the test will display a negative result.
Despite Patient 1's second sample being positive for cancer, patient 1 is more than likely without cancer and this repetition is due to an error like contamination. More testing would be necessary to find out.